The lymphatics are an extensive unidirectional system of blunt-ending vessels that regulate normal tissue pressure by retrieving excess fluid from the interstitium, transporting it to regional lymph nodes, and returning it to the venous system by way of the thoracic…
Angiosarcoma Angiosarcomas are malignant tumors that recapitulate many of the functional and morphologic features of normal endothelium. They vary from highly differentiated tumors resembling a hemangioma to anaplastic lesions difficult to distinguish from a poorly differentiated carcinoma or pleomorphic sarcoma.…
Vascular Tumors of Intermediate Malignancy The term hemangioendothelioma is the designation for vascular tumors that have a biologic behavior intermediate between a hemangioma and a conventional angiosarcoma. Tumors included in this group have the ability to recur locally and some…
The term hemangioma has been used broadly in the past to describe any benign, nonreactive vascular process with an increase in normal or abnormal-appearing vessels or simply abnormally configured vessels. Hemangiomas have been further subclassified pathologically, based on the predominant…
During the 1930s and 1940s, the diagnosis of adult or pleomorphic rhabdomyosarcoma was increasingly made, and most of the rhabdomyosarcomas reported during this period were of this type. These tumors occurred mainly in the muscles of the lower extremity and…
Striated Muscle Tissue: Development and Structure Skeletal muscle is formed primarily within myotomes, which are arranged in segmental pairs along the spine and make their first appearance in the cephalic region during the third week of intrauterine life. In the…
Originally viewed as smooth muscle tumors (leiomyoblastomas), it is now known that gastrointestinal stromal tumors ( GISTs ) arise from interstitial cells of Cajal (ICCs) or ICC precursor cells. ICCs are pacemaker cells centered on the myenteric plexus along the…
Leiomyosarcomas account for 5% to 10% of soft tissue sarcomas. They are principally tumors of adults but are far outnumbered even in this age group by more common sarcomas, such as liposarcoma and undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma). Likewise,…
To a large extent, the distribution of benign smooth muscle tumors parallels the distribution of smooth muscle tissue in the body. The tumors tend to be relatively common in the genitourinary and gastrointestinal tracts, less frequent in the skin, and…
Liposarcoma, accounting for 15% to 25% of all sarcomas, is the most common sarcoma of adults. There are several subtypes, which are histologically, biologically, and cytogenetically distinct from one another ( Table 14.1 ). These subtypes range in behavior from…